BB84 protocol using rotationally symmetric states and a Fresnel cone

Area of Science:

• Quantum Information Science
• Quantum Cryptography
• Optical Physics

Background:

• Quantum Key Distribution (QKD) protocols like BB84 rely on the uncertainty principle for security.
• Photon polarization is commonly used in QKD, but requires a shared reference frame, challenging for mobile or satellite systems.
• Existing reference-frame-independent QKD methods using vector beams are often wavelength-dependent, limiting bandwidth.

Purpose of the Study:

• To demonstrate a proof-of-principle BB84 protocol that is reference frame invariant.
• To overcome the limitations of wavelength dependency in previous rotationally symmetric QKD systems.
• To enable secure quantum communication in dynamic scenarios like satellite-to-satellite links.

Main Methods:

• Implemented a classical BB84 protocol using rotationally symmetric vector beams as mutually unbiased bases.
• Employed a Fresnel cone-based measurement system for detecting photon polarization.
• Verified the system's performance in a proof-of-principle demonstration.

Main Results:

• Achieved a low quantum bit error rate (QBER) of 1.1%.
• Demonstrated reference frame invariance, eliminating the need for a shared coordinate system.
• Showcased wavelength-independent operation, preserving bandwidth capabilities.

Conclusions:

• The developed system is suitable for QKD in scenarios with rotating reference frames, such as satellite or handheld communication.
• This approach offers a path towards secure, high-bandwidth quantum communication in dynamic environments.
• The reference frame invariant and wavelength-independent nature of this QKD protocol enhances its practical applicability.